I've noticed over the last month or so that my boy Spangle (around 18 months old) has a kind of weird appearance at the end of his tail. Instead of stopping bluntly, in a kind of rounded point (as I've seen in all other rats), it has a very small spiky part coming out of the end. At first I was worried it was somehow the end of the bone coming out, but I've felt it and it feels more soft and there's 100% not been any injuries to his tail. It doesn't cause him pain when I touch it either. It's just a tiny white spike. Is this normal?

If you're reasonably certain it's not a degloved tip (which is unlikely anyway) it's probably just what's sometimes called 'tail nail'. As I understand it, it's a buildup of keratin that some rats get sometimes on their tail tip; some of my rats have it and it's never been a problem.